Ozone and Reactive Oxygen Species

High tropospheric ozone (O3) concentrations affect plant growth and crop yield. O3 enters leaves through stomata and rapidly degrades in the apoplast into other reactive oxygen species (ROS), which readily interact with surrounding biomolecules. Due to their high reactivity, ROS act as important signalling molecules. Apoplastic ROS perception induces secondary ROS production in other cellular compartments and activates interorganelle signalling pathways towards stress defence. Defence responses include activation of hormonal signalling, the enhancement of antioxidative defence responses, protection of the photosynthetic machinery and induction of cell death processes. Different species prioritise different defence strategies and population studies towards the identification of genetic loci associated with O3 tolerance are currently the most promising approach for identifying genes involved in O3 tolerance.